The Crime Scene. Chapter 2 Johnston High School Forensics

Transcription

1 The Crime Scene Chapter 2 Johnston High School Forensics

2 Learning Goals 1) Lesson 1: Define physical evidence, Discuss responsibilities of first officer arriving at scene, Explain steps to be taken to thoroughly record crime scene 2) Lesson 2: Describe proper procedures for conducting systematic search for evidence, Describe proper techniques for packaging common types of physical evidence 3) Lesson 3: Define and understand concept of chain of custody, Know the controls collected from the CS, Understand the process of submitting evidence to the laboratory 4) Lesson 4: Understand steps taken to maintain safety standards at the crime scene, Understand legal considerations at the crime scene

3 Lesson 1 1) Define physical evidence 2) Discuss responsibilities of first officer arriving at scene 3) Explain steps to be taken to thoroughly record crime scene

4 Physical Evidence Physical Evidence: Any object that can establish that a crime has been committed or can link a crime to its victim or its perpetrator.

5 Importance of Evidence Forensic Science begins at the crime scene! Scientist must be able to RECOGNIZE evidence Must be able to COLLECT evidence Must be able to PRESERVE evidence Remember garbage in, garbage out!

6 Common Types of Evidence Fingerprints DNA, body fluids Hairs/Fibers and other trace evidence Notes, signatures Firearms, bullets, cartridge casings, tool marks Drugs and drug paraphernalia metals, glass, paint, soil charred debris, explosive devices Digital 6

7 Common Sources of Evidence 7

8 Approaching a Crime Scene

9 Securing and Isolating Crime Scene The first officer at the scene must 1) offer medical assistance when needed and/or make an arrest 2) exclude all unauthorized personnel from scene (very hard!) 3) Call for assistance/backup 4) isolate area (tape, barricades) Must try to preserve and protect area as much as possible

10 Once Secured Lead investigator evaluates area Determines boundaries Establishes perpetrator s path (entry and exit) Obvious evidence documented and photographed Initial walk-through & develop strategy for examination

11 Recording the Scene Goal: Thoroughly document scene in a timely manner an untouched state while preserving all evidence Records useful for investigation/court Cases may go to court months/years later!

12 Recording the Crime Scene Photographs Sketches Notes

13 PHOTOGRAPHY Take unaltered! Do not move evidence until picture is taken! If moved, must be recorded in notes All photos must show position and location to crime scene Close ups of smaller items must be taken Use a ruler or scale to note size Videotaping also useful

14 Photography Scene Multiple views Entrances Exits Evidence Close ups Perspectives Multiple angles Windows

15 Sketches After photographing make a rough sketch Drawn at crime scene Contains accurate depictions of dimensions of scene (use tape measurer) Shows location of all objects having bearing on the case

16 Rough Sketch - Tools Paper Pencil Measuring Tape Ruler Clipboard Eraser Compass 16

17 Finished Sketch Done carefully, attention to appearance Must reflect rough sketch (admissible in court) Computer Aid Drafting (CAD) -software for reconstructing Drawn to scale

18 Rough Sketch to Final bsapp.com

19 Rough vs Finished Sketch

20 Notes Match to sketch Constant activity Quick, short, bulleted What can you not see from the photo? Helpful for long-term cases - memory Identifies all evidence what is it? Who collected? Tape recording used sometimes

21 What should be noted? These notes must identify: Time an item of physical evidence was discovered Who discovered it? How and by whom it was packaged and marked Disposition of an item after it was collected May be the only source of information for refreshing one s memory

22 Lesson 2 1) Describe proper procedures for conducting systematic search for evidence 2) Describe proper techniques for packaging common types of physical evidence

23 The Search for Evidence - Strategy thorough and systematic type depends on the size and locale of the scene # of collectors participating in the search investigator trained to not overlook any pertinent evidence. Physical evidence can be anything from massive objects to microscopic traces.

24 Search Patterns

25 Search Patterns

26 The Search Evidence Collection Locate evidence that links suspect to crime and/or suspect to victim Often, most evidence is clearly visible, BUT Others can only be detected via examination in the lab Must collect ALL possible carriers of trace evidence Clothing Vacuum sweepings Rug samples Fingernail scrapings

27 Beyond the Crime Scene Search for evidence must extend to secondary CSs or the autopsy room Medical examiner determine COD Tissues and organs retained for pathological and toxicological examination Medical examiner secures a variety of items for investigator

28 Evidence the ME sends to Investigator Victim s clothing Fingernail scrapings Head and pubic hairs Blood (for DNA analysis) Vaginal, anal, and oral swabs (sex-related crimes) Recovered bullets from body Hand swabs from shooting victims (GSR)

29 Collecting & Packaging Evidence Goal: handle evidence so that there is least amount of change from CS to lab Potential problems Contamination Breakage Evaporation Accidental scratching/breaking Loss via carelessness Integrity = evidence kept intact (ex. Hair, soil should be left on clothing)

30 Tools for Evidence Collection Boxes Evidence Submission Forms Paper Bags Sealable containers Sealing Tape Swabs Plastic Bags Sharpies & Pens Forceps Gloves

31 Other Tools Unbreakable plastic pill bottles w/ pressure lids Manila envelopes, screw-cap glass vials, metal pill boxes Clean, unused paint cans

32 How do you know which to use? Trace Evidence (Hairs, fibers, glass) unbreakable pill bottles, screw cap glass vials, metal pill boxes Druggist Fold - good for trace and powders (Collecting Hairs/fibers) Charred Debris from a Fire Clean unused paint can prevents evaporation of volatile petroleum residues 32

33 How do you know which to use? Biological Material disposable tools Breathable containers (paper bags, manila envelops) prevents accumulation of moisture, preventing mold growth Air dry and package separately Red BIOHAZARD sticker across seal 33

34 How do you know which to use? DNA Evidence Contamination concern face mask, lab coat, disposable gloves and forceps Sterile cotton swab (moisten swabs for dried blood) multiple swabs Air dry sample and keep refrigerated How to collect DNA samples (blood) 34

35 Some general rules Ordinary mailing envelopes should be avoided Sealable plastic bags often universal container Thoroughly label Signature across the seal

36 If evidence is found on large structure (door, wall) remove specimen with forceps With blood, scrape off surface, transfer to moistened swab, or cut out area bearing stain

37 Most Important Point About Evidence Collection Each different item or similar items collected at different locations must be placed in separate containers! Prevents damage through contact Prevents cross contamination

38 Lesson 3 1) Define and understand concept of chain of custody 2) What controls are collected from the scene, suspects, or victims? 3) Understand the process of submitting evidence to the laboratory

39 Chain of Custody Chain of Custody = a list of all people who came into possession of an item of evidence Must be established for use in court Everyone must be accounted for! Each person must obtain written record of acquisition and disposition Each person may be required to testify in court If not, authenticity and integrity of evidence is lost

40 Collecting Standard/Reference Samples Standard/Reference Sample: Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime-scene evidence Can also be obtained from victim Paint from a hit-and-run vehicle

41 Example of SRS Your crime scene unit locates and dusts prints from a crime scene 41

42 Other Controls Buccal Swab swab from the inner portion of the cheek, performed to collect cells for use in determining the DNA profile of an individual Substrate Control Uncontaminated surface material close to area where physical evidence has been deposited Used to ensure that the surface on which a sample has been deposited does not interfere with lab results Used in arson cases has surface been exposed to accelerant?

43 Submit Evidence to Lab Delivered personally or by mail depending on case and urgency Person familiar with case Can t ship certain chemicals/live ammo/explosives Need evidence submission form Nature of crime, victim, case#, agency, investigator Brief description of case List of evidence What to investigate for each time

44 Evidence Submission Form

45 RI Evidence Submission Forms Department of Health RISCL 45

46 Lesson 4 1) Understand steps taken to maintain safety standards at the crime scene 2) Understand legal considerations at the crime scene

47 Crime Scene Safety Risks Dangers of firearms, sharp instruments Chemical and Biological Hazards Anthrax Blood Borne Pathogen (BBP) Diseases AIDS/HIV Hepatitis B Universal Precautions Treat every biological fluid as if it harbors a BBP Wear Personal Protective Equipment (PPE)

48 Legal Considerations at the CS Search and Seizure of Evidence Must conform to Fourth Amendement The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizure, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized. When can a warrantless search be performed? emergency circumstance to prevent the immediate loss or destruction of evidence following an arrest, evidence found on or around the person or with consent from the parties involved

49 Applicable Cases 1) Mincey v. Arizona (1978) Four day search at a homicide scene without warrant home of Rufus Mincey - suspected drug dealer, law enforcer killed undercover Police illegally seized drugs, paraphernalia, bullets Mincey appealed and court ruled on side of Mincey 2) Michigan v. Tyler (1978) * Business leased by Loren Tyler was destroyed by fire * Conditions prevented police to search until the next day * Four separate searches made - each without a warrant * Evidence seized was used to convict Tyler of conspiracy * Court overturned his conviction